A mineral salt such as a magnesium chloride (called “Nigari” in Japan) and a calcium chloride works as a tofu coagulant and is used for producing tofu. And a glucono-δ-lactone that is a coagulating component is gluconic acid working as a tofu coagulant and used for producing tofu. It is skilful to make high quality tofu of such a fine texture, a good touch with teeth and tongue, and a good taste. Particularly, magnesium chloride and gluconic acid have a very fast reaction rate with soymilk, and exhibit difficulty in producing the high quality tofu constantly, shown in patent document 4 (JP 3553690B1). Thus, fat and an emulsifier are mixed in a magnesium chloride solution for making emulsified coagulant as water in oil (W/O) type, which emulsified coagulant is commercially available, for example. And, a tofu coagulant which is comprised of magnesium chloride, polyglycerol esters of fatty acids as the emulsifier, and diglyceride, is disclosed in patent document 2 (JP 2908633B1). Diglyceride (DG) and Diacylglycerol (DAG) are the same. And, a tofu coagulant which is comprising a mineral salt coagulant, polyglycerol esters of fatty acids, and fat, is disclosed in patent document 3 (JP 2912249B1).
The above commercially available emulsifier tofu coagulant comprises Nigari, which has a good slow-acting character and which is used in manufacturing tofu products at high temperature solidification and popularized. The commercially available emulsifier tofu coagulant is used preferably for mass production scale at a tofu factory, because it induces stable product quality, low loss, and high working-efficiency. However, some consumers feel a peculiar flavor that is different from the original tofu flavor, and increase a uniform flavor of tofu products to lose distinctive regional production of the same character by different manufacturers. Moreover, the commercial emulsifier tofu coagulant is 5 or 6 times more expensive than normal Nigari. The occasion of the recent economic downturn rises fuel and soybean costs and, wholesale price down pressure has been forced, in addition to having to use an expensive tofu coagulant. Thus, tofu manufacturers' economic burden becomes more and more. For reducing tofu costs, so that a tofu manufacturer doesn't use the expensive tofu coagulant as much as possible to provide consistent high-quality tofu production. Furthermore, since the commercial emulsifier tofu coagulant includes synthetic emulsifiers and stabilizers, it has a good slow-acting character, but it is necessary to use with high-power emulsifying dispersion a machine for good dispersion. Therefore, sometimes dispersion level of the commercial emulsifier tofu coagulant is low and tofu products lost or amount of the commercial emulsifier tofu coagulant is much and tofu products are deteriorated during the distribution process. In recent years, as the global boom in Japanese food, tofu is a situation where demand is growing by the principal natural food, especially among vegetarians. Especially in the West, has increased the demand for organic products, processed food in Japan is about 60% organic soy milk and tofu products that situation would. In the future, tofu products, consisting of natural raw materials are expected to continue to increase as the representative of the expected natural food without any synthetic chemical food additive.
The assignee herein obtained patent grant and issuance of a tofu manufacturing method in patent document 1 (JP 3654623B1) which is given in the device configuration and does not use emulsifiers as additives. However, in actual exploitation, since an applicable scope is narrow, there has been a case where sufficiently satisfactory high-quality tofu is not obtained depending on selection and a combination of the kinds of food oil and the concentrations of Nigari. For reducing the cost of W/O type emulsified coagulant, it is necessary to use less oil, reduce the amount of an aqueous phase, and use an aqueous Nigari solution of higher concentrations, for example. However, use of high-concentration Nigari can stabilize the emulsion and increase the viscosity of the emulsion depending on the emulsifying conditions, but it is difficult to make optimal and stable emulsified phase affected by heat such as a friction heat, thus practical slow-acting coagulation reaction being hard to obtain. In use of Nigari concentration in less than 2M, inconvenience (demulsification) resulting from exotherm and increased emulsion viscosity is less obvious.
Studies on W/O type emulsion characteristics that use salt water and processed fat (main component: 80% or more of DAG) and do not use an emulsifier as an additive, are made and disclosed in related art document 2 and related art document 5. But, in those related art documents 2 and 5, slow-acting character is not evaluated as a tofu coagulant, and the concentration of a magnesium chloride solution is 0.5M or less, and it is not affected by heat such as friction heat. And it is only evaluated that salt water phase and oil phase ratio is 1:1. Other conditions herein are that unit M is the molar concentration per liter of a solution, that the concentration of magnesium chloride solution used herein is about 10% w/w in terms of magnesium chloride hexahydrate crystal of molecular weights of approximately 203 and that the specific gravity is approximately 1.036. If using as coagulation of soymilk a diluted salt solution, the aqueous phase increases and it is necessary to increase the amount of fat, thus resulting in that this is not economical. DAG is a fat which is the same as conventional triacylglycerol (TAG). DAG is a fat component that is comprised of a number of commercial vegetable oils such as olive oil, as disclosed in related art document 6.
The assignee filed an application for a tofu manufacturing method that uses an emulsion obtained by stirring and mixing a coagulant solution and a culinary fat containing DAG having an oil phase of 1% or more, or uses a tofu coagulant which is a cooled, stirred and mixed water-in-oil type (W/O type) emulsion brought to a temporarily stable W/O type emulsion state without adding any emulsifier and which attains a slow-acting effect of soymilk coagulation reaction (patent document 6). And, a continuous emulsification device for dressing is disclosed in patent document 7. Generally, dressing is an O/W type emulsion. And, an O/W type emulsion for margarine or chocolate which does not use an emulsifier is disclosed in patent document 8. Generally, margarine and chocolate are solid foods that stabilize culinary fat with a high melting point by crystallization of the culinary fat. A W/O type emulsion which comprises artificial 1,2-DAG of not less than 50% in DAG is disclosed in patent document 9. But, related art document 7 shows that a ratio of 1,2-DAG versus 1,3-DAG is 3:7 in natural fat.